Solid-film lubricants



United States Patent 2,991,206 SOLID-FILM LUBRICANTS Paul D. Miller and Richard A. Jeiferys, Columbus, Ohio,

assignors, by mesne assignments, to The Battelle Development Corporation, Columbus, Ohio, a corporation of Delaware N Drawing. Filed Dec. 26, 1957, Ser. No. 705,121 Claims. (Cl. 148-615) This application is a continuatiornin-part of our copend-ing application Serial No. 389,871, filed November 2, 1953, and now abandoned. The invention rel-ates to lubricants for titanium, and titanium-containing alloys. More particularly, this invention relates to solid-film lubricants that are applied to prepared surfaces of titanium, and titanium-containing alloys; and articles of titanium, and titanium-containing alloys, comprising a basis material, a surface coating, and a solid-film lubricant.

It is well known that the fabrication and use of titanium, and titanium-containing alloys, present certain severe and inherent difficulties. Of particular difiiculty are the poor antigalling and antiseizing properties of such metals when they are subjected to reciprocal, rotary or shaping forces and pressures, especially when their surfaces are in loaded contact with another metal surface.

It is known that heating titanium, and titanium-containing alloys, in air tends to reduce the galling and seizing properties inherent in such metals when brought into contact with another metal surface in the presence of a lubricating film and subjected to light-reciprocating, low-rotary, and limited-shaping forces and pressures. The reduction in galling and seizing properties is due to the formation of a thin oxide film on the surface of the base metal. This oxide film functions to separate the metal surfaces and retain the lubricant, thereby reducing the tendency to gall and seize when subjected to lightreciprocating forces, low-rotary speeds and forces, and limited-shaping forces and pressures. However, the separation of the metal surfaces continues only so long as the relatively thin oxide film is not destroyed by the abrasion of foreign particles, rough surfaces, or by merely wearing away.

Thus, even though a lubricating film is placed between a heat-treated titanium surface and another metal surface, the lubricant does not eliminate galling and seizing properties.

In our copending application, Serial No. 384,341, filed October 5, 1953, and issued December 16, 1958, as Patent No. 2,864,732, there is disclosed and claimed an invention which relates to surface preparation of titanium, and titanium-containing alloys. More particularly, the invention relates to chemically active baths for treating said surfaces, and toprocesses utilizing said baths, and articles of titanium, and titanium-containing alloys treated thereby.

The chemically active bath is further disclosed as an aqueous bath solution comprising a halide, at least one salt selected from the group consisting of phosphates, borates, oxalates, citrates, and tartrates of alkali and alkaline earth metals, and a halogen acid. Articles of titanium, and titanium-containing alloys may be treated with the aforesaid aqueous bath solution by immersion, dipping, spraying, or other suitable means; the aqueous bath solution being stirred, agitated, heated, or cooled, as required. There is also disclosed, if required, the process step of furnacing the treated metal articles in a gaseous atmosphere at a temperature of from 600 F. to 1000 F. for a period of from one to five hours.

The preparation of the surfaces of titanium, and tita- Ilium-containing alloys, in accordance with the disclosure ine of the aforementioned copending application results in superior and improved antiseizing and antigalling properties.

The use of molybdenum disulfide M08 as a hightemperature, low-coefiicient-of-friction, solid-film lubricant is well known. Not only does MoS reduce sliding and shearing friction under severe conditions of temperature and load, but it is superior to graphite for many purposes. M08 is stable in the normal atmosphere, or, in the absence of oxygen, over a wider range than liquid lubricants. Its lubricating performance is explained on the basis of its structure. Each lamina of M08 is com posed of a sheet of molybdenum atoms with a sheet of sulfur atoms on each side. When M08 is applied to a metal surface, the strong sulfur-to-metal bond holds each lamina strongly to the metal surface whereas the weak, sulfur-to-sulfur bond lets the laminae of MoS slip easily over each other.

Lubrication is sustained for only so long as the M08 film remains between the rubbing surfaces in effective amounts. When M08 is applied to unprepared surfaces of titanium, and titanium-containing alloys, regardless of the bonding vehicle or material used, the life of the effective film is short. Films which are long lived under light loads at low speeds have been formed on steel, aluminum, brass, stainless steel, and glass surfaces by bonding the M05 thereto with liquid vehicles, such as asphaltand silicone-base varnishes, glycerine, ethylene glycol, polyglycol ether, and even corn syrup and dextrose. However, none of these bonding vehicles enable the formation of a long-lived, effective film on the surfaces of titanium, and titanium-containing alloys, especially when they are subjected to extremely highpressures and high speeds.

Therefore, it is an object of this invention to provide a lubricant for surfaces in frictional contact with each other.

Further, it is an object of this invention to provide a solid-film lubricant that can be applied to the surface of titanium, and titanium-containing alloys, and which will form a long lived effective film of M08 Still further, it is an object of this invention to provide a method for improving the antigalling and antiseizing properties of titanium, and titanium-containing alloys.

Still further, it is an object of this invention to provide articles of titanium, and titanium-containing metals that exhibit improved antigalling and antiseizing properties.

Further objects and advantages of the present invention will be apparent in view of the following detailed disclosure and description thereof.

The present invention relates to a solid-film lubricant comprising a suspension of molybdenum disulfide in an epoxy phenolic resin combination, which is applied to prepared surfaces of titanium and titanium-containing alloys, air dried and then cured by application of heat.

The suspension or mixture of MoS in the epoxy phenolic resin combination bonding vehicle is made by mixing MoS with the epoxy phenolic resin combination in the presence of a suitable dispersing medium.

Suitable dispersing mediums include normally liquid organic compounds which are active solvents for the resins and mixtures of these solvents with diluents. These normally liquid organic compounds, which are solvents, include, but are not limited thereto, the following: ketones such as methyl isobutyl ketone, methyl ethyl kctone, cyclohexanone, mesityl oxide, etc.; ethers and ether-esters of glycols such as monomethyl, monoethyl, and monobutyl ether of ethylene glycol, and propylene glycol and the corresponding acetates and propionates; halogenated hydrocarbons such as ethylene dichloride, trichloroprane, etc. Liquid aromatic compounds, such as benzene, toluene, xylene, etc., and alcohols such as ethanol, butanol, and methyl isobutyl carbinol are also useful constituents for dispersing mediums and function primarily as diluents for active solvents.

The molybdenum disulfide, M08 should be in a finely divided form, preferably a powder, and in a state of high purity. The amount of molybdenum disulfide suspended in the epoxy phenolic resin combination may be varied over a wide range. The molybdenum disulfide should be present in an amount suificient to impart desired lubricating properties. The resin combination should be present in an amount sufficient to firmly bond the M05 particles to the extent necessary for the particular application. Preferably for the better results the suspension of M05 in the resin combination bonding vehicle is preschlorhydrin in basic medium at about 50 to 150 C. with the use of more than one equivalent of epichlorhydrin for each phenolic hydroxyl group of the phenol and with a slight stoichiometric excess of a base, such as S 5 dium or potassium hydroxide. The polyepoxide resins may be obtained from the reaction of dihydric phenols with epichlorhydrin in basic medium or from the direct addition reaction of dihydric phenols and aliphatic diepoxides.

Representative of polyepoxide resins which are particularly advantageous for use in the solid-film lubricant compositions of the invention are resins resulting from the reaction of bis-phenol, epichlorhydrin and alkali, such as sold under the trade name Epon by the Shell Chemical Corporation, having the following typical structure:

ent in the ratio of one part of M08 to about 1-3 parts of the total amount of resins in the epoxy phenolic resin combination.

The epoxy phenolic resin combination used as the bonding vehicle may be defined as a catalyzed resin combination of from 40 to 90 percent polyepoxide resins and from 10 to 60 percent phenolic resins. The polyepoxide resins impart flexibility and adhesion to the resin combination, while the phenolic resins impart hardness. Depending on the antigalling and antiseizing requirements for a particular application and the ratio of M08 to the resin combination, the polyepoxide resins and phenolic resins may be present in amounts somewhat different than the aforesaid stated amounts which are preferred. Such a resin combination contains a catalyst for curing purposes.

Known curing catalysts may be utilized in the above resin combinations. These catalysts include phosphoric acid, dicthylene triamine, butyl dihydrogen phosphate, and p-toluenesulfonic acid, although other curing catalysts may be used. Ordinarily with the aforementioned cata lyst materials and other acidic catalyst materials, about 0.2 to 5 parts by weight of the catalyst are employed per part by weight of the total amount of resins in the resin combination.

Advantageously a butylated urea formaldehyde resin may be used as a curing catalyst in an amount varying from 2 to percent of the epoxy phenolic resin combination and may replace in part or in whole conventional catalysts in the catalyzed resin combination. Such butylated urea formaldehyde resins are available commercially. For example, Uformite F-240, sold by the Resinous Products & Chemical Company (Rohm & Haas Company) is a suitable butylated urea formaldehyde resin. This resin is available in the form of a solution containing 60 percent solids in a solvent made up of 40 percent xylol and 60 percent butanol, has a specific gravity of about 1.02, and an acid number of 3-8.

The suitable polyepoxide resins may be fulther defined as complex polymeric reaction products from the reac tion of a polyhydric phenol with epichlorhydrin in a basic medium. Such complex polyepoxide polymeric reaction products are characterized by having terminal aliphatic epoxide groups and being free from reactive groups other than epoxide and aliphatic hydroxyl groups and may be represented by the general formula:

wherein 11 indicates the degree of polymerization and is an integer of the series 0, 1, 2, 3 R represents the residue of the polyhydric phenol, R represents an aliphatic radical containing at least one aliphatic hydroxyl group, and R is a terminal aliphatic radical containing a terminal epoxide group. These polyepoxide resins may be obtained by reacting a polyhydric phenol with epi- These Epon resins have reactive hydroxyl and epoxy groups and vary in their melting point and epoxide equivalent, e.g., a resin melting at 64-76, having an epoxide equivalent (grams of resin containing 1 equivalent of epoxide) of 450-525 (Epon 1001); a resin melting at 97-103, having an epoxide equivalent of 905-985 (Epon 1004); a resin melting at 127-133, having an epoxide equivalent of 16004900 (Epon 1007); and a resin having an epoxide equivalent of 24003000 (Epon 1009);

etc.

United States Patent No. 2,774,748, Howard et 211., discloses polyepoxide resins under the terminology of glycidyl polyether of a polyhydric phenol and details examples of their preparation that further illustrate suitable polyepoxide rains for incorporation in the solidfilm lubricant composition of the invention.

The suitable phenolic resins may be further defined as unsaturated liquid phenolic resins, such as an unsaturated ether of a methylol phenol, which have compositions corresponding to the general formula:

eat)- -(CI-Iz0H)n H-y-H wherein n is an integer from 1 to 3 inclusive, and R represents an organic radical derived from the class of compounds containing a reactive C=C group, such as vinyl, allyl, methylallyl, cyclopentyl, cyclohexenyl, styryl, etc., as Well as halogenated derivatives of the aforementioned groups. These phenolic resins are described more fully in US. Patents 2,579,329, 2,579,330, and 2,579,331.

Representative of suitable methylol phenol ethers are such ethers of 2,4,6-tris-(hydroxy methyl) phenols, and phenol aldehyde condensates containing reactive hydroxyl groups which may be derived from mononuclear phenols,

polynuclear phenols, monohydric phenols or polyhydric phenols. United States Patent No. 2,521,911, Greenlce, discloses suitable representative phenol aldehyde condensates.

Particularly advantageous as unsaturated liquid phenolic resins are the unsaturated ethers of tris-(hydroxy methyl) phenol having the general formula:

HOH H OH 20 C 2 CHzOH in which R is an unsaturated aliphatic radical, and more particularly the allyl radical or group, i.e., the allyl ether of tris-(hydroxy methyl) phenol, as described in aforementioned patents. This phenolic resin, namely the allyl ether of tris-(hydroxy methyl) phenol may vary somewhat in its proper-ties and may contain small and varying amounts of the allyl ether of monohydroxy methyl phenol and dihydroxy methyl phenol.

Such a liquid unsaturated phenolic resin, sold under the trade name R-l08 by the General Electric Company, is a commercial allyl ether of tris-(hydroxy methyl) phenol. It has a density of around 1.15 to 1.25; a solidifying point below 50 F.; a boiling range which begins at approximately 400 F. with simultaneous polymerization; a molecular weight of approximately 200, which is soluble in polar solvents, and has a viscosity of 2000-4000 cp. at 25 C. This resin is an intermediate resin distinguished from other phenolic resins in that it produces cured films When baked, which have remarkable resistance to alkali. Its loW molecular weight and unsaturated aliphatic group allows more reactivity with the epoxide resins than other conventional phenolic resins.

The epoxy phenolic resin combination has been defined as a resin combination of from about 40 to 90 percent of the aforedescribed polyepoxide resins and from about to 60 percent of the aforedescribed phenolic resins. Such resin combinations are prepared by mixing the polyepoxide resin and the liquid phenolic resin. If desired, either or both of the resins may be dissolved in suitable solvents, that have been mentioned aforehand and are well known in the art, to facilitate this mixing. Additional solvents or solvents and diluents may be added, if desired, to obtain a lubricant of suitable properties (e.g. viscosity, solids content) for the particular manner of application.

Illustrative of suitable epoxy phenolic resin combinations, but not limited thereto, are epoxy phenolic resin combinations disclosed in US. Patents 2,774,748, Howard et al., and 2,816,084, Nowacki. The patent to Howard et al. discloses a composition of matter cured with the aid of acidic curing agents to a resinous product, which composition of matter comprises a mixture of glycidyl polyether of a polyhydric phenol having a 1,2-epoxy equivalency greater than 1.0, and a 2-alkenyloxybenzene having 1 to 3 methylol groups which are linked singly at the 2, 4 and 6 positions on the benzene ring. The patent to Nowacki concerns coating compositions made with a combination of an epoxide resin and a specially unsaturated liquid phenolic resin, and advantageously, also with a small amount of a butylated urea formaldehyde resin.

Other substances than the essential components, namely M05 and the catalyzed epoxy phenolic resin combination, for the solid film lubricant may be incorporated therein in minor amounts provided superior antigalling and ant-iseizing properties may be obtained. Already mentioned are the use of suitable dispersing mediums and diluents. Other conventional materials such as pigments, other resins, plasticizers, fillers, and dyes may also be tolerated in the solid film lubricant, but only in minor or insignificant amounts.

The lubricant composition may be applied to the specially prepared surfaces of titanium and titanium alloys by any of the conventional methods for applying liquid or paste compositions (e.g. brushing, spraying, dipping, immersion, etc.).

The air drying of the applied lubricant should be carried forth at such temperatures and for such a length of time that the applied lubricant coating is non-tacky to the touch. Generally such drying causes removal of substantial proportions of the dispersing medium from the applied suspension of molybdenum disulphide in the epoxy phenolic resin combination. With certain of the more volatile organic liquids, ordinary room temperatures are sufficient. Preferably the applied suspension is air dried for 1 to 36 hours at room temperature. If sufficient air drying of the applied lubricant is not permitted, bubbles or voids may be found in the cured solid-film lubricant.

The curing of the applied air dried lubricant is accomplished by application of heat thereto. Cures may be accomplished at temperatures from about 250 F. to 450 F. with the time needed for a complete cure being less at the higher temperatures. In general, completeness of cure may be shown by the development of an increasing insolubility of the cured product in methyl ethyl ketone, which is a good solvent and dispersing medium for the uncured lubricant. Preferably the cure is accomplished by heating in an oven or furnace for from 1 to 36 hours at 250 F. to 350 F., although thin coats of the solid-film lubricant on titanium metals may be cured in about 5 minutes at about 450 F.

The stability at elevated temperatures, the adherence to a prepared surface of titanium, and titantium-containing alloys, and the retention of M05 particles, properties which the epoxy phenolic resin combinations exhibit, make them particularly well adapted for use as the bonding vehicle in the practice of the invention.

The combination of the titanium basis material having the specially prepared surface coating and the solid-film lubricant thereon provide novel articles having properties heretofore unobtainable. The article of the combination of the titanium basis material, the specially prepared surface coating, and the solid-film lubricant of the invention provides antigalling and antiseizing properties superior to the sum of the antigalling and antiseizing properties of the components.

The titanium, and titanium-containing alloys, hereinafter referred to simply as titanium metal, are defined as pure, unalloyed titanium or titanium-base alloys. Examples of suitable alloying elements include: manganese, aluminum, molybdenum, vanadium, tin, iron, nitrogen, oxygen, copper, and chromium. Other refractory metals, such as zirconium and its alloys, could be treated by the practice of this invention.

The surface of the titanium metal is prepared by treating the surface with an aqueous, chemically active bath solution comprising a halide, at least one salt selected from the group consisting of phosphates, borates, oxalates, citrates, and tartrates of alkali and alkaline earth meta-ls, and a halogen acid.

The halide of the aqueous, chemically active bath may be defined as a binary compound of fluorine, chlorine, bromine, or iodine, with an element or radical. In the practice of this invention, it has been found that halides of the alkaline metals and alkaline earth metals are satisfactory. Potassium fiuoride, potassium chloride, and sodium fluoride have been found to be particularly adapted for use in the subject bath.

The salt used in the aqueous, chemically active bath has been previously described as being selected from the group consisting of phosphates, borates, oxalates, citrates, and tartrates of alkali and alkaline earth metals. In the practice of this invention, it has been found that, when one or more of the acid hydrogens of the acid have been replaced by an alkali or alkaline earth metal, satisfactory results are obtained. Tribasic sodium phosphate, dibasic sodium phosphate, potassium dihydrogen phosphate, sodium tetraborate, and sodium metaborate have been found to be particularly well adapted for use in the subject bath.

The halogen acid may be hydrofluoric acid, hydrochloric acid, bromic acid, or iodic acid. Hydrofiuoric and hydrochloric acids have been found to be particularly well adapted for use in the subject bath. The halogen acid need not be the same as the halogen of the halide.

Further, each of the above three groups of bath ingredients can be used singly or in combination with others of the same group. p

In the use of the aqueous, chemically active bath, the temperature range may satisfactorily be from about 15 C. up to C. However, if a temperature lower than 25 C. is used, the immersion time becomes unduly long and the quality of the coating may be lessened. The pH of the bath should not be greater than 6.8.

The surface of titanium metal that has been treated with the aqueous, chemically active bath solution has thereon a surface coating having a filmlike gray appearance. The surface coating is soluble in HCl, HNO HF, concentrated NaOH, and boiling H O. The surface coating demonstrates high adsorption affinities for nonviscous fluids, such as lubricating oils, inks, dyes, and paints. The surface coatings are substantially alkali or alkaline earth metal, titanium, halide coatings. The surface coating contains substantial proportions of titanium, at least one metal selected from the group consisting of the alkali and alkaline earth metals, and a halide, and a minor amount of a nonmetallic radical selected from the group consisting of phosphate, borate, citrate, oxalate, and tartrate, all in chemically combined form on the surface of the titanium metal.

The surface of the titanium metal should be clean and free of any scale or oxide prior to immersion in the bath. If the titanium metal has a grease film covering the surface, it has been found that the use of a hot sodium metasilicate degreasing bath prior to treating in the stripping bath will remove such a grease film and facilitie the action of the stripping bath. An HFHNO bath will satisfactorily remove scale or oxide subsequent to the degreasing. The compositions of the above degreasing and stripping baths were set forth only for the purpose of aiding one skilled in the art to practice the subject invention, and are not intended to limit the claims hereinafter set forth to the use of specific degreasing and stripping baths as herein illustrated. Any such baths that will prepare a clean surface free of oxide and scale will be satisfactory in the practice of this invention.

Untreated titanium and titanium alloys have virtually no resistance to galling and seizing. Titanium metal, having the surface coating from treatment with the aqueous, chemically active bath solution when used in conjunction with conventional lubricants has sufiicient resistance to galling and seizing so that it may be drawn through dies to form wires, although it cannot withstand high loads for appreciable lengths of time. Titanium metal, having the surface coating from treatment with the aqueous, chemically active bath solution and having thereon the solidfilm lubricant of the invention can withstand high loads for appreciable lengths of time.

The following examples of the practice of this invention are set forth only for the purpose of illustrating said invention and are not to be construed as limiting or restricting it thereto.

In the examples set forth below, reference will be made to the following titanium and titanium-containing alloys: RC-55 is pure titanium metal. RC130A contains 7% manganese, the balance being titanium. RC- 130B contains 4% manganese, 4% aluminum, the balance being titanium. Ti-75A contains 0.1% iron, 0.02% nitrogen and traces of oxygen, the balance being titanium. Ti-150A contains 1.3% iron, 0.02% nitrogen, 0.25% oxygen, 0.2% carbon, and 2.7% chromium, the balance being titanium.

The specimens of titanium metal referred to in the examples were 0.5 inch diameter, 0.5-inch thick, and machined and lapped to optical flatness.

EXAMPLE I Specimens of RC-55, RC-130 and Ti-75A were degreased and cleaned. They were then immersed in a fluoride-phosphate bath solution having the following composition of ingredients per liter of aqueous solution: 20 g./l. KF-ZH O, 50 g./1. Na PO -12H O and 11.5 ml./l. HF solution (HF of a concentration 50.3% by weight was used in all of the bath solutions set forth by way of example, unless otherwise indicated). The pH of the bath was 5.2. The length of the immersion was 10 minutes at a temperature of C. An analysis of of the coating formed on the surface of the test specimens indicated the following average percent by weight composition; Ti 16.6, Na 8.5, K 24.7, F 38.8, and P0 3.1%, the balance being indeterminable by standard analytical procedures.

A suspension of one part by weight of M08 powder, 99.9% pure, was made in two parts by weight of unpigmented Synthetasine 100, available from Synthetasine Protective Coatings, Inc., 600 Fifth Avenue, New York, N.Y., using sutficient methyl ethyl ketone as a solvent so as to form a thick, pastelike mixture. Unpigmented Synthetasine is a composition of the type more fully disclosed in US. Patent 2,816,084, Nowacki. More particularly, Synthetasine 100 comprises a combination of an epoxide resin and a specially unsaturated liquid phenolic resin with a butylated urea formaldehyde resin, all in a mixture of methyl isobutyl ketone and methyl ethyl ketone. The epoxide resin, Epon 1007 (Shell Chemical Corporation), the specially unsaturated liquid phenolic resin, R-108 (General Electric Company), and the butylated urea formaldehyde resin, Uformite 240 (Rohm & Haas Company), are present in the unpigmented Synthetasine 100 in about 87.5 parts of Epon 1007, 56.6 parts Rl08, and 21.9 parts Uformite 240 in a mixture of about 70 parts of methyl isobutyl ketone and about 17.5 parts of methyl ethyl ketone.

The lubricant mixture was applied to the prepared surface of the specimens by dipping, and the specimens were air dried for 12 hours at room temperature. The specimens were then placed in an oven and cured for 12 hours at 300 F.

EXAMPLE II The surfaces of the RC-55, RO-l30B and Ti-75A specimens were prepared according to Example I by degreasing, cleaning, and immersing in the fluoride-phosphate bath solution.

A suspension of one part by weight of M05 powder in three parts by weight of unpigmented Synthetasine 100 was made up as shown by Example I.

The lubricant mixture was applied to the prepared surface of the specimens by dipping and the specimens were air dried for eight hours at room temperature. The specimens were then placed in an oven and cured for eight hours at 300 F.

EXAMPLE III The surfaces of the RC-SS, RC-B and Ti-75A specimens were prepared according to Example I by degreasing, cleaning, and immersing in the fluoridephosphate bath solution.

A suspension of one part by weight of MOS; powder and one part by weight of unpigmented Synthetasine 100 was made up as shown by Example I.

The lubricant mixture was applied to the prepared surface of the specimens by dipping and the specimens were air dried for six hours at room temperature. The specimens were then placed in an oven and cured for ten hours at 300 F.

EXAMPLE IV Specimens of RC 55, 130A, 130B, Ti-75A and Ti- 15OA were degreased and cleaned. They were then immersed in a fiuoride-borate bath solution having the following composition of ingredients per liter of aqueous solution: 18 g./l. KF-ZH O, 40 g./l. Na B O -10H O, and 16 ml./l. HF solution. The pH of the bath was 6.4. The length of immersion was 20 minutes at a temperature of 85 C. An analysis of the coating formed on the surface of the test specimens indicated the following average percent by weight composition: Ti 29.9, Na 7.4, K 24.2, F 35.9, and B 0; 0.5 percent, the balance being indeterminable by standard analytical procedures.

A suspension of one part by weight of MoS powder and two parts by weight of unpigmented Synthetasine 100 was made up as shown by Example I.

The lubricant mixture was applied to the prepared surface of the specimens by dipping and the specimens were air dried for 12 hours at room temperature. The specimens were then placed in an oven and cured for 12 hours at 350 F.

EXAMPLE V Test specimens of RC-55 and T i-75A were degreased and cleaned. A suspension of one part by weight of M08 powder and two parts by weight of unpigmented Synthetasine 100 was made up as in Example I.

The lubricant mixture was applied to the unprepared surface of the specimens by dipping and the specimens were air dried for one hour at room temperature. The specimens were then placed in an oven and cured for 12 hours at 300 F.

EXAMPLE VI Test specimens of RC-SS and Ti-75A were degreased and cleaned. The test specimens were then introduced into a tube furnace and heated to a temperature of 800 F. for a period of five hours. During the heating there was a constant circulation of outside air through the furnace.

A suspension of one part by Weight of MoS powder and two parts by weight of unpigmented Synthetasine 100 was made up as shown in Example I.

Following this furnacing or heat treatment, the lubricant mixture was applied to the heat-treated surface of the specimens by dipping and the specimens were air dried for four hours at room temperature.

The specimens were then placed in an oven and cured for six hours at 300 F.

EXAMPLE VII Test specimens of RC-SS were degreased and cleaned. The test specimens were then immersed in a fluoridephosphate bath solution having the composition illustrated in Example I to prepare coatings on the surface of the test specimens according to the method of Example I. The test specimens were then furnaced by heating in a gaseous atmosphere at about 800 F. for about 19.5 hours. These specimens were prepared for comparative test purposes and no solid-film lubricant was applied to the prepared surfaces of the specimens.

Lubricant films on the surface of titanium metals may be evaluated by different types of tests. A very severe test may be made on a high-speed rotary-wear machine.

Data obtained from tests from improved rotary-wear properties are set forth below in Table I. The tests were conducted with an apparatus in which two 0.5-inch diameter test specimens were worn under oil against a 4.5 inch diameter steel disk which rotated at a linear speed of 910 feet/minute. The test specimens were weight loaded so as to bring the specimens directly against the rotating disk under the full weight load. The actual pressure of the test specimens varied, as indicated in Table I. The apparatus was run until the lubricant film on the surface coating broke down causing the specimens to gall on the rotating steel disk and automatically shutting off the apparatus. Unprepared test specimens that were not treated with solid-phase lubricant and bonding vehicle immediately galled on the rotating disk.

The steel disk was a 1045 steel plate, hardened to 50 Rockwell C. The test specimens in each test were Ti-75A unless noted otherwise. Test specimen No. 1 was prepared as shown in Example I; No. 2 was prepared as shown in Example II; No. 3 was prepared as shown in Example III; N0. 4 was prepared as shown in Example IV; No. 5 was prepared as in Example V; No. 6 was prepared as in Example VI, and No. 7 (Ti RC-55) was prepared as in Example VII.

Table 1 Test Specimen Number Duration of Load Rotation (p.s.i.)

273.5 hours 700 42 hours 600 199 hours 800 68 hours 600 40 minutes 600 44 minutes 600 400 minutes 600 Articles of titanium metal comprising the basis material, surface coating, and the solid-film lubricant clearly exhibit new and novel properties over titanium articles not made according tothis invention. The results given in Table I illustrate that titanium metal materials, test specimens Nos. 1-4, having the prepared surface coating and the solid-film lubricant of the invention thereon have rotary-wear properties that are superior and are many times greater than the rotary-wear properties of titanium metal materials, test specimens Nos. 5-7, that do not have the combination of the prepared surface coating and the solid-film lubricant thereon.

This invention represents, so far as is known, the first instance of the use of M08 and an epoxy phenolic resin combination as a solid-film lubricant for titanium metals. Further, this invention represents the first instance of the application of a solid-film lubricant to the surface of titanium metal that has been prepared by treatment with an aqueous chemically active bath solution containing a halide and at least one salt selected from the group consisting of phosphates, borates, oxalates, citrates, and tartrates of alkali and alkaline earth metals, and a halogen acid.

Articles composed of, or fabricated from, titanium metal, the surfaces of which have been treated by the practice of this invention, will be useful in any application where the surfaces of titanium or titanium-containing metal articles are to be put in loaded contact with another titanium or metal surface. The prepared surfaces will be particularly useful in applications where it is necessary that there be a lubricant phase present to lower the friction between surfaces in loaded contact with each other.

While the particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the appended claims are intended to cover all such changes and modifications as follow within the true spirit and scope of this invention.

What is claimed is:

1. A method of treating titanium metal to prepare a composite article of titanium metal having two coatings thereon imparting antigalling and antiseizing properties thereto, the method comprising the steps of: contacting the surface of the titanium metal with an aqueous, chemically active bath solution consisting essentially of a halide, at least one salt selected from the group consisting of phosphates, borates, oxalates, citrates, and tartrates of alkali and alkaline earth metals, and a halogen acid so as to form a coating thereon, the coating containing in chemically combined form a major amount of titanium, a metal selected from the group consisting of the alkali and alkaline earth metals, and a halide, and a minor amount of a radical selected from the group consisting of phosphate, borate, oxalate, citrate, and tartrate radicals; and applying to said coating a solid-film lubricant consisting essentially of a suspension of MoS in a thermosetting catalyzed epoxy phenolic resin combination.

2. The method of claim 1 in which the solid-film lubricant consists essentially of one part by weight MoS in one to three parts by weight of the epoxy phenolic resin combination.

3. A method of treating titanium metal to prepare a composite article of titanium metal having two coatings thereon imparting antigalling and antiseizing properties thereto, the method comprising the steps of: contacting the surface of the titanium metal with an aqueous, chemically active bath solution consisting essentially of a halide, a sodium phosphate salt, and a halogen acid so as to form a coating thereon, the coating containing in chemically combined form a major amount of titanium, sodium, and a halide, and a minor amount of the phosphate radical; and applying to said coating a solid-film lubricant consisting essentially of a suspension of M03 in a thermosetting catalyzed epoxy phenolic resin combination.

4. A method of treating titanium metal to prepare a composite article of titanium metal having two coatings thereon imparting antigalling and antiseizing properties thereto, the method comprising the steps of: contacting the surface of the titanium metal with an aqueous, chemically active bath solution consisting essentially of a halide, a potassium borate salt, and a halogen acid so as to form a coating thereon, the coating containing in chemically combined form a major amount of titanium, potassium, and a halide, and a minor amount of the borate radical; and applying to said coating a solid-film lubricant consisting essentially of a suspension of M08 in a thermosetting catalyzed epoxy phenolic resin combination.

5. A composite article of titanium metal having two coatings thereon imparting antigalling and antiseizing properties thereto, the composite article comprising: titanium metal selected from the group consisting of titanium, and titanium-base alloys; a coating on the surface of said titanium metal containing, in chemically combined form, a major amount of titanium, a metal selected from the group consisting of the alkali and alkaline earth metals, and a halide, and a minor amount of a radical selected from the group consisting of phosphate, borate, oxalate, citrate, and tartrate; and a solid-film lubricant consisting essentially of a suspension of MoS in a thermosetting catalyzed epoxy phenolic resin combination, adhering to said coating.

6. The composite article of claim 5 in which the solidfilm lubricant consists essentially of a suspension of one part by weight MoS in one to three parts by weight of the epoxy phenolic resin combination.

7. A composite article of titanium metal having two coatings thereon imparting antigalling and antiseizing properties thereto, the composite article comprising: titanium metal selected from the group consisting of titanium, and titanium-base alloys; a coating on the surface of said titanium metal containing, in chemically combined form, a major amount of titanium, sodium, and fluoride, and a minor amount of phosphate; and a solid-film lubricant consisting essentially of a suspension of one part by weight M08 in one to three parts by weight of a thermosetting catalyzed epoxy phenolic resin combination, adhering to said coating.

8. A composite article of titanium metal having two coatings thereon imparting antigalling and antiseizing properties thereto, the composite article comprising: titanium metal selected from the group consisting of titanium, and titanium-base alloys; a coating on the surface of said titanium metal containing in chemically combined form, a major amount of titanium, sodium, and fluoride, and a minor amount of borate; and a solid-film lubricant consisting essentially of a suspension of one part by weight MoS in one to three parts by weight of a thermosetting catalyzed epoxy phenolic resin combination, adhering to said coating.

9. A composite article of titanium metal having two coatings thereon imparting antigalling and antiseizing properties thereto, the composite article comprising: titanium metal selected from the group consisting of titanium, and titanium-base alloys; a coating on the surface of said titanium metal containing, in chemically combined form, a major amount of titanium, sodium, potassium, and fluoride, and a minor amount of phosphate; and a solidfilm lubricant consisting essentially of a suspension on one part by weight M05 in one to three parts by weight of a thermosetting epoxy phenolic catalyzed resin combination consisting of from 40 to 90 percent polyepoxide resins and from 10 to percent phenolic resins, adhering to said coating.

10. A composite article of titanium metal having two coatings thereon imparting antigalling and antiseizing properties thereto, the composite article comprising: titanium metal selected from the group consisting of titanium, and titanium-base alloys; a coating on the surface of said titanium metal containing, in chemically combined form, a major amount of titanium, sodium, and fluoride, and a minor amount of borate; and a solid-film lubricant consisting essentially of a suspension of one part by weight MoS in one to three parts by Weight of a thermosetting epoxy phenolic catalyzed resin combination consisting of from 40 to percent polyepoxide resins and from 10 to 60 percent phenolic resins, adhering to said coating.

References Cited in the file of this patent UNITED STATES PATENTS 2,541,027 Bradley Feb. 13, 1951 2,588,234 Henricks Mar. 4, 1952 2,686,155 Willis Aug. 10, 1954 2,703,768 Hall Mar. 8, 1955 2,816,084 Nowacki Dec. 10, 1957 2,864,732 Miller et al. Dec. 16, 1958 FOREIGN PATENTS 676,029 Germany May 24, 1939 756,859 Great Britain Sept. 12, 1956 OTHER REFERENCES Am. Machinist, June 11, 1951, page 152. 

1. A METHOD OF TREATING TITANIUM METAL TO PREPARE A COMPOSITE ARTICLE OF TITANIUM METAL HAVING TWO COATINGS THEREON IMPARTING ANTIGALLING AND ANTISEIZING PROPERTIES THERETO, THE METHOD COMPRISING THE STEPS OF: CONTACTING THE SURFACE OF THE TITANIUM METAL WITH AN AQUEOUS, CHEMICALLY ACTIVE BATH SOLUTION CONSISTING ESSENTIALLY OF A HALIDE, AT LEAST ONE SALT SELECTED FROM THE GROUP CONSISTING OF PHOSPHATES, BORATES, OXALATES, CITRATES, AND TARTRATES OF ALKALI AND ALKALINE EARTH METALS, AND A HALOGEN ACID SO AS TO FORM A COATING THEREON, THE COATING CONTAINING IN CHEMICALLY COMBINED FORM A MAJOR AMOUNT OF TITANIUM, A METAL SELECTED FROM THE GROUP CONSISTING OF THE ALKALI AND ALKALINE EARTH METALS, AND A HALIDE, AND A MINOR AMOUNT OF A RADICAL SELECTED FROM THE GROUP CONSISTING OF PHOSPHATE, BORATE, OXALATE, CITRATE, AND TARTRATE RADICALS, AND APPLYING TO SAID COATING A SOLID-FILM LUBRICANT CONSISTING ESSENTIALLY OF A SUSPENSION OF MOS2 IN A THERMOSETTING CATALYZED EPOXY PHENOLIC RESIN COMBINATION. 